package com.xx.utils;

import org.springframework.stereotype.Component;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;

/**
 * @program:
 * @description: 雪花算法代码实现
 * @author: xx
 **/
@Component
public class IdWorker {    // 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
    private final static long twepoch = 1288834974657L;    // 机器标识位数
    private final static long workerIdBits = 5L;    // 数据中心标识位数
    private final static long datacenterIdBits = 5L;    // 机器ID最大值
    private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);    // 数据中心ID最大值
    private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);    // 毫秒内自增位
    private final static long sequenceBits = 12L;    // 机器ID偏左移12位
    private final static long workerIdShift = sequenceBits;    // 数据中心ID左移17位
    private final static long datacenterIdShift = sequenceBits + workerIdBits;    // 时间毫秒左移22位
    private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;    private final static long sequenceMask = -1L ^ (-1L << sequenceBits);    /* 上次生产id时间戳 */
    private static long lastTimestamp = -1L;    // 0，并发控制
    private long sequence = 0L;    private final long workerId;    // 数据标识id部分
    private final long datacenterId;    public IdWorker(){        this.datacenterId = getDatacenterId(maxDatacenterId);        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }    /**
     * @param workerId
     *            工作机器ID
     * @param datacenterId
     *            序列号
     */
    public IdWorker(long workerId, long datacenterId) {        if (workerId > maxWorkerId || workerId < 0) {            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }        if (datacenterId > maxDatacenterId || datacenterId < 0) {            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }        this.workerId = workerId;        this.datacenterId = datacenterId;
    }    /**
     * 获取下一个ID
     *
     * @return
     */
    public synchronized long nextId() {        long timestamp = timeGen();        if (timestamp < lastTimestamp) {            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }        if (lastTimestamp == timestamp) {            // 当前毫秒内，则+1
            sequence = (sequence + 1) & sequenceMask;            if (sequence == 0) {                // 当前毫秒内计数满了，则等待下一秒
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }
        lastTimestamp = timestamp;        // ID偏移组合生成最终的ID，并返回ID
        long nextId = ((timestamp - twepoch) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift) | sequence;        return nextId;
    }    private long tilNextMillis(final long lastTimestamp) {        long timestamp = this.timeGen();        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }        return timestamp;
    }    private long timeGen() {        return System.currentTimeMillis();
    }    /**
     * <p>
     * 获取 maxWorkerId
     * </p>
     */
    protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuffer mpid = new StringBuffer();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();        if (!name.isEmpty()) {            /*
             * GET jvmPid
             */
            mpid.append(name.split("@")[0]);
        }        /*
         * MAC + PID 的 hashcode 获取16个低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }    /**
     * <p>
     * 数据标识id部分
     * </p>
     */
    protected static long getDatacenterId(long maxDatacenterId) {        long id = 0L;        try {
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);            if (network == null) {
                id = 1L;
            } else {                byte[] mac = network.getHardwareAddress();
                id = ((0x000000FF & (long) mac[mac.length - 1])
                        | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                id = id % (maxDatacenterId + 1);
            }
        } catch (Exception e) {
            System.out.println(" getDatacenterId: " + e.getMessage());
        }        return id;
    }

    public  String nextIdStr() {
        return Long.toString(this.nextId());
    }
}
